A known means of improving thermal resistance of exterior concrete building walls involves using thermally insulating plastic foam panels as exterior sheathing. While suitable for below ground applications, this means has shortcomings in above ground installation. For example, exposed thermal insulation panel portions can be unsightly. In addition, exposed thermal insulation panel portions may degrade as a result of the weather.
An alternate means, which overcomes shortcomings due to exposed thermal insulation panel portions, provides a composite wall by embedding a thermal insulation panel between two layers of concrete. In building composite walls of this type, one begins with by setting into place spaced-apart rigid forms that define a cavity bounded by wall surfaces. One continues by placing a thermal insulation foam board having opposed major planar surfaces into the cavity to divide the cavity into two subcavities. Pouring concrete into the subcavities yields the composite wall after concrete curing and form removal. Punching connectors through the foam at approximately 12 inch (30.5 centimeter (cm)) intervals before pouring concrete into the subcavities forms a securely connected sandwich of the foam board between the concrete layers after the concrete has cured.
In order to prevent distortion or bursting of the thermal insulation boards, a customary practice involves pouring the concrete in stages, alternating between subcavities to balance forces applied by the weight of the concrete on the opposite sides of the foam boards or panels. For example, a 9 foot wall (2.7 meters (m)) may be formed by pouring concrete into a subcavity on one side of the foam board to a height of about 3 feet (0.9 m), then pouring concrete into a second subcavity on the other side of the foam panel to a height of about 6 feet (1.8 m), then pouring concrete to a height of about 9 feet (2.7 m) in the first subcavity, and then filling the remainder of the second subcavity. Pouring the concrete for composite concrete and foam board walls in stages is undesirable because, at the conclusion of each stage, it is generally necessary to stop pouring concrete, reposition equipment, and begin pouring the next stage. These steps can add significantly to the time required to construct the composite walls. It would be more desirable if the cavities on the opposite sides of the thermal insulation board could be filled with concrete without regard to balancing forces applied by the weight of the concrete on the opposite sides of the insulation panel.